Process to produce microfibrillated/nanofibrillated cellulose by impacts

Abstract

The present invention relates to a process to produce highly microfibrillated cellulose (MFC) and nanofibrillated cellulose (NFC). The invention also refers to a microfibrillated/nanofibrillated cellulose produced according to such process. The microfib-rillated/nanofibrillated cellulose is obtained by subjecting a cellulose fiber in a slurry of cellulose pulp to multiple mechanical impacts. The cycle may be repeated several times. Non-cutting bars disposed in a ring formation is the preferred configuration. At least two rings concentrically arranged facing each other in high rotation transmit the kinetic energy to the fibers to provide the highly defibrillated microfibrillated/nanofibrillated cellulose.

1 . A process to produce a highly microfibrillated/nanofibrillated cellulose, which process comprises the steps of:
 a) providing a slurry comprising cellulose fibers,   b) subjecting the slurry to defibrillation under continuous impacts to produce microfibrillated/nanofibrillated cellulose.   
     
     
         2 . The process according to  claim 1  wherein the microfibrillated/nanofibrillated cellulose is returned as a slurry to step a) to another defibrillation step b). 
     
     
         3 . The process according to  claim 1  wherein the impacts are provided by non-cutting bars. 
     
     
         4 . The process according to  claim 1  wherein the impacts are provided by non-cutting bars in a rotor, in a stator or in both. 
     
     
         5 . The process according to  claim 1  wherein the non-cutting bars are projections in the rotor, the stator or in both. 
     
     
         6 . The process according to  claim 1  wherein a non-cutting bar alternate with a bar gap in the rotor, the stator or in both. 
     
     
         7 . The process according to  claim 1  wherein the bar gap between two non-cutting bars in the same ring is at least 1 mm. 
     
     
         8 . The process according to  claim 1  wherein the non-cutting bars have a bar gap in a ring disposition at the rotor, the stator or in both. 
     
     
         9 . The process according to  claim 1  wherein one of the rotor, the stator, or both, is rotating. 
     
     
         10 . The process according to  claim 9  wherein the rotor ring and the stator ring rotate in contrary directions. 
     
     
         11 . The process according to  claim 1  wherein the bars are rotating at a linear speed of at least 20 m/s. 
     
     
         12 . The process according to  claim 1  wherein the non-cutting bars at the rotor and the non-cutting bars at the stator are disposed concentrically to produce a ring gap of at least 0.2 mm between the bars at the rotor and the bars at the stator. 
     
     
         13 . The process according to  claim 1  wherein the slurry is subjected to continuous impacts under controlled temperature from 30 to 100° C. 
     
     
         14 . The process according to  claim 1  wherein the fibers are cellulose fibers, Kraft fibers, bleached cellulose fibers, semi-bleached cellulose fibers, unbleached cellulose fibers; dry cellulose fibers, never dry cellulose fibers or mixtures thereof. 
     
     
         15 . The process according to  claim 1  wherein the fibers are microfibrillated cellulose, nanofibrillated cellulose, or mixtures thereof. 
     
     
         16 . The process according to  claim 15  wherein the fibers are processed with disc refiners, conical refiners, or combinations thereof. 
     
     
         17 . The process according to  claim 1  wherein the slurry comprises a consistency from 2.0 to 8%. 
     
     
         18 . The process according to  claim 1  wherein at least one pH modifier is added to the slurry, so that modified microfibrillated/nanofibrillated cellulose is formed. 
     
     
         19 . The process according to  claim 18  wherein the pH modifier will produce a slurry having a pH from 4.0 to 9.0. 
     
     
         20 . The process according to  claim 18  wherein the pH modifier is selected from the group consisting of ammonia, sodium hydroxide, potassium hydroxide, sodium hypochlorite, acetic acid, phosphoric acid, nitric acid, hydrochloric acid and sulfuric acid. 
     
     
         21 . Microfibrillated/nanofibrillated cellulose produced according to the process of  claim 1 . 
     
     
         22 . Microfibrillated cellulose produced according to the process of  claim 1  having a diameter in from 0.01 μm to 0.8 μm. 
     
     
         23 . Microfibrillated cellulose, according to  claim 22 , having an average diameter of 0.1 μm, determined by scanning electron microscopy. 
     
     
         24 . Microfibrillated cellulose, according to  claim 22 , wherein at 0.85% wt. in water comprises a dynamic viscosity from 15-1000 mPas·s. 
     
     
         25 . (canceled)